The hypothesis of this application is that differential O-glycosylation of MUC-1 mucin contributes to the detachment of cancer cells from a primary cancer and mediates attachment at metastatic sites. The hypothesis will be assessed by three specific aims. The first will identify various forms of the MUC-1 mucin that interact with the matrix protein. The second specific aim will characterize the oligosaccharide and protein structure of MUC-1 mucin that interact with matrix proteins. The third specific aim will characterize the MUC-1 mucins that interact in breast cancer with normal human lung endothelial cells.